Marek Stasikowski

At NewStore I took on responsibilities to salvage and refine multiple customer facing services, including micro-frontends. My most notable initiatives and actions:

• Highlighting to the engineering community strategies of using characterisation tests as a way of managing a large legacy codebase, and unblocking progress towards developing a new feature with an estimated $6 million ARR.
• Leaving areas of multiple codebases in a better shape than I found them.
• Driving design of circuit breaker patterns for both queues and synchronous entry points. I've created and communicated to the staff+ engineers a comprehensive RFC, inviting feedback and emphasising its significance and impact on engineering resources. This eventually dropped in priority due to the approaching Black Friday/Cyber Monday period.
• For the BFCM preparations I drove hands-on efforts to load test select flows of the NewStore platform, collecting evidence of bottlenecks and improving performance of parts of the system, reducing pressure on database clusters and queues. Apart from that, ensured good observability and per-flow dashboards being implemented, enabling efficient diagnostics and operations.
• Focused on identifying the proverbial 20% of effort that leads to 80% of the outcome whilst collaborating on code bases.
• Disseminating core principles of extreme programming and industry standards in software engineering, like fast feedback loops, single responsibility, importance of refactoring, test-first approaches, low coupling, reduction of business logic proliferation.
• Speaking at weekly knowledge sharing sessions, presenting on topics like working with legacy codebases, types of testing and when to use them, tracking work progress based on cycle time and predicting future outcomes based on historic evidence.
• Project Bouncer: a weekly hackathon effort to create a robust process of provisioning per-tenant, ephemeral support accounts for inspecting individual customer accounts.

Key technologies used:

• AWS
• Terraform
• Kubernetes
• CI/CD using GitLab
• TypeScript
• React
• Python
• Go
• OpenSearch
• RabbitMQ

Marks & Spencer

October 2024 - February 2025

I've joined the M&S engagement as a platform engineer. During my time here, I have:

• Researched and documented the "new web project onboarding" process from a product focused perspective, informing future efforts to make it as easy as possible for teams to migrate to a standardised platform. This would benefit teams so that they could prioritise the product over software delivery mechanisms.
• Worked with the team to design and manage an effective code freeze around the golden quarter, i.e. Christmas, which helped dozens of teams stay productive even though their code would not be making it into production for a while.
• Kicked off work towards making mutation testing a new capability of the platform. This would help teams identify overlaps and gaps in their safety nets.

After a year of work on various facets of CMC's tech landscape as a consultant, I was permanently hired as Principal Software Engineer.

Within the Onboarding squad, while continuing my previous duties, I've also been pushing to migrate away from a legacy Java monolith towards an AWS lambda based approach, in line with company strategy. This effort was designed to create a distributed, modern backend setup to implement sign-up functionalities.

I would consistently advocate XP specific practices like:

• Relying on code quality tools like SonarQube or various linters
• TDD (think tools like Jest, JUnit)
• BDD, to ensure specific scenarios were implemented as necessary from a business perspective (using Cypress, Cucumber)
• CI/CD, so that every delivered batch of code was up to par with what was expected of it (I've used GitHub workflows and Jenkins for that)
• Frequent code checkins, to minimise friction between parallel streams of work
• Gathering feedback from stakeholders to ensure a correct trajectory of what was being built

Staying abreast of requirements often meant delving into legacy Java services, extending them in an environment where an asynchronous, message based architecture was at the heart of a company-wide architecture. The stack consisted of:

• Spring
• ActiveMQ
• Oracle SQL
• Protobuf
• RxJava

CMC Markets was one of the first companies out there to offer online trading services.

I've joined to help shape conventions and streamline areas of code within a sizeable (100k+ SLOC) React/Redux sign-up application. It was built using different approaches by many people prior which resulted in significant bottlenecks and made it necessary to clear tons of tech debt.

I would also work on an Angular app used to manage all things related to a customer's account. This required extending and creating new logic built on top of Angular's approach to state management utilising reactive programming (RxJS).

My main activities included:

• helping to shape the architecture of a sizable, multi-dimensional onboarding application
• mentoring other developers
• advocating XP and CI practices
• integrating with 3rd party APIs
• contributing to service architecture design
• extending existing Java services

At Global Relay I was a practitioner of an agile approach to software. I collaborated closely with a product owner, QA engineer and fellow software engineers to continuously deliver small chunks of business value-adding code. I was involved in the process from inception to delivery.

I mostly pair programmed to achieve high levels of transparency and confidence in the delivered product.

I've been mostly using React and Redux to build products. For some more complex logic, we've also used Xstate to make state changes more formalised and predictable.

I also organised regular sessions across the London community to practice TDD, solving classic katas like word-wrap, finding prime factors or Minesweeper.

My contributions and expertise had been recognised and I became an acting team lead in December 2021.

As team lead, I've championed ways of working in spirit of the agile manifesto. I strived to minimise process and red tape. I was looking after every team member's concerns, holding weekly one-to-ones. I worked closely with the product owner to understand expectations of the business. I have implemented regular product reviews to allow team members to own and demonstrate their achievements, and for stakeholders to witness progress.

My proud achievement was taking away time pressure from engineers and communicating estimates by using lead time based Monte Carlo projections rather than individually conceived timelines.

A trunk based and feature flag focused release process ensured visibility to both QA as well as the product owner. Transparency was our core value.

Pret a Manger

January 2020 - April 2020

I was the first engineer to join the effort of re-platforming Pret's tech stack.

I designed and got stakeholders' approval for a system to enable a redefined online presence. The new platform was built on top of a headless CMS, and a hybrid approach of statically generated and server-side rendered pages, hosted in an automatically scaling, Docker-based environment within Google Cloud Platform.

SPYSCAPE is an espionage museum and collection of interactive experiences and games, based in New York. The results of the games played are used to build up a psychological profile which the visitors can further explore on SPYSCAPE's website.

I joined to help extend and maintain the games and online profiles of visitors, implementing new ways of browsing through their "takeaway videos", exposing parts of their profiles in social media, and exploring their data in meaningful ways.

I joined Equal Experts as a JavaScript consultant to their client engagements.

John Lewis & Partners

August 2018 - July 2019

At John Lewis, the online department store, I was working on all things React: the My Account section, FAQs, auth.

I also mentored and upskilled JL Partners, helping them understand my craft better and build front end apps themselves.

Klarna

April 2018 - July 2018

Hailing from Sweden, Klarna provides payment processing implemented through a dozen micro-services, built mostly on top of Node.js, Ruby, and some more esoteric solutions. I joined the Authentication & Personalisation team to take ownership and reverse engineer as well as provide out of hours support for services inherited from another team.

My previous experience in building universal apps proved to be useful at uSwitch. In an effort to phase out a dated, tech debt heavy Ruby on Rails app, we rebuilt it page by page using a React/Node stack, while constantly integrating with the rest of the legacy platform.

notonthehighstreet.com hired me to help them rebuild their checkout pages. Constantly pairing, we put together a self-contained, isomorphic universal front end service on top of Node.js. Using that approach we implemented some other features on the site as separate front end services.

With that experience, I gave talks about building universal front ends at various meetups in London, and at ReactJS Day in Verona.

I was involved in working directly with and at international clients' offices, fitting solutions to existing infrastructures.

I also ran a one-stop shop for anything front end/JavaScript related, creating prototypes of applications, both mobile and desktop, as well as Node.js APIs.

At Cigna I was building travel and life insurance policy configurators in a team of four AngularJS developers.

In Pearson's Data Analytics and Visualization team I worked on an internal big data analysis platform.

• developing a Node.js API to query Elasticsearch, cache results and expose a simple API to clients
• building UIs to break down a sea of data into more meaningful pieces and present them in the form of numbers and charts

At SiteSell I worked remotely with a Canadian team on a website building solution for people not familiar with web technologies.

• developing rich components for a complex website building interface, adhering to MVC principles
• building "file" managers like Mac Finder/Windows Explorer with drag and drop, toolbars with various item operations, batch operations, uploading multiple files AJAX style, etc.

This position was at the corporation's main software house, building applications for global clients. I designed information architecture and built UI mockups for new applications, and implemented front ends for internal applications.

My first full-time job at a website building company at the largest interactive media agency in Poland.